Handover mechanisms in next generation heterogeneous wireless ...

PROXY BASED AUTHENTICATION LOCALISATION SCHEME FOR HANDOVER
not be overheard by the sAN. The sAN forwards these session key renew credentials to
the MH. If N m that is included in the key renew response is valid, the MH generates
another mobile nonce N m ' , and establishes the new session key PMK’ according to
Equation 6.7. The newly issued nonce N m ' will be delivered to the FAP as shown in
Figure 6.7. Based on the two new nonces N m ' and N p ' , the FAP can derive the
corresponding PMK’. Later on, the derived PMK’ is provided to the AN for updating
the session key.
E
LAK
( Nm
|| Ns
')
ELAK
( Nm
')
- 127 -
E
pa
E
{ ELAK
( Nm
|| Ns
')}
pa
{ ELAK
( Nm
')}
EK (PMK'
)
pa
Figure 6.7 Session key renewal procedure initiated by AN
In this thesis, it is assumed that the communications between a MH and an AN are
always protected by other link layer security mechanisms. For example, IEEE 802.11i
[42] defines how the PMK can be utilised to ensure a secure association with an access
point.
6.4 Security Analysis for the PBAL
In the proposed PBAL scheme, the authentication authority is temporarily relayed to a
third-party entity FAP when a mobile subscriber roams outside the territory of its home
network. The FAP plays a similar role as the Visitor Location Register (VLR) of 3GPP
in verifying a mobile user’s identity using the home-supplied authentication vectors, as